THE OLD WOELD MONKEYS . 51 Hands and Feet,—All Cercopithecidse have pent a-dactyl hands and feet. The palms and soles are hairless, and have traces of all primitive pads except the FIG. 11.—The skulls of the lower Primates. A, Lemur macaco: A', Mandible of Lemur macaco showing incisor, canine and first premolar teeth; A", Front of skull of Lemur showing gap hetween the incisor teeth; B, Tarsius spectrum; G, Cebus fatuellus ; D, Jlfa-cacus rJiesus : E, Cusps of upper molar teeth; F, Cusps of lower molar teeth; E.A.M., External auditory meatus; N.L.D., Naso-laehrymal duct; P.G.P., Post-glenoid process; P.W.O., Posterior wall of orbit; S.M.F., Spheno-maxillary fissure; T.A., Tympanic annulus; T.B., Tympanic bulla. Lebters on tooth cusps explained in text. thenar pad of the proximal group. The entire surface is traversed by papillary ridges, so the tactile sense is very well developed. All fingers and toes have flat nails, and syndactyly is present in the Mangabeys.